For manual transmission vehicles that are fitted with automated Stop-Start control of the engine it is desired to maximize fuel economy by utilizing automated engine shut downs and restarts whenever possible. Stop-in-Neutral (SIN) Stop-Start systems are currently employed in the market place but these systems do not maximize fuel economy since many drivers wait in gear in a stationary vehicle. SIN stops are not invoked under these conditions and a Stop-in-Gear (SIG) strategy is required.
However to employ a Stop-in-Gear (SIG) Stop-Start strategy, it is necessary to ensure that the driveline is disengaged. SIG stops and starts may typically be invoked if both the clutch and brake pedals are depressed with the transmission in gear. However, if a driver-induced restart request is received from, for example, releasing of the brake pedal, the Stop-Start logic must only be allowed to crank the engine if the driveline is disengaged as this prevents the vehicle jerking or moving during cranking. Therefore current practice is to use a very conservative clutch pedal position threshold for the clutch pedal position that must be achieved if stopping of the engine is to be permitted.
There are two disadvantages with the use of such a conservative clutch pedal position threshold.
Firstly, if the driver allows the clutch pedal to move back in a clutch engaging direction while the engine is stopped (Pedal creep) then the engine cannot in some cases be restarted because the clutch pedal position will have traversed the clutch pedal position threshold to permit the engine to be restarted.
Secondly during take-off from rest it is common practice for a driver to begin to engage the clutch at the same time as the brake pedal is released and the driver is beginning to depress the accelerator pedal. If the timing of these events by the driver is slightly off, the driver can inadvertently allow the clutch pedal to move too rapidly in the clutch engaging direction thereby causing the clutch pedal position to traverse the clutch pedal position threshold before cranking has commenced and preventing the engine from being restarted.
In both cases opportunities for starting the engine are missed and the driver may be unsatisfied with the operation of the Stop-Start system to such an extent that they will switch it off.